A known turbocharger compressor housing comprises a compressor housing and a diffuser that is press fit into a sleeve portion of the compressor housing. An impeller moves air through the diffuser and into the compressor housing.
FIGS. 2A-2C illustrate a prior art turbocharger compressor housing having a longitudinal axis 106 and comprising a compressor housing 102 and a diffuser 104. The compressor housing 102 comprises an interior wall 105 with a sleeve portion 108 having a cylindrical wall surface 109 that is sized to receive a cylindrical insert portion 110 of the diffuser. The cross-sectional dimension of sleeve portion 108 in the region of surface 109 is sized to be slightly less than the cross sectional dimension of a wall surface portion 112 of the insert portion 110 of the diffuser. As a result, when these components are pressed together, an interference fit, indicated at 114 in FIG. 2C, is provided that extends about the entire periphery of the insert 110. FIG. 2C illustrates this prior art construction with the insert portion of the diffuser 104 shown in a fully inserted position into the compressor housing 102. When in this position, a clearance gap 117 is provided between a sloping wall surface 116 of compressor housing 102 and a sloping wall surface 118 of diffuser 104. Also, as can be seen in FIG. 2A, compressor housing 102 is provided with an annular surface 120 that acts as a stop by engaging an annular surface 124 of the diffuser 104 to limit the extent the diffuser is inserted into the compressor housing.
With this construction, a low pressure area 130 exists at the air entry side of the diffuser. In contrast, high pressure areas 132, 134, at a higher pressure than the low pressure area, exist at a high pressure side of an impeller, thereby creating a pressure differential across the interference fit 114 which can result in pressure equalization leakage across the interference joint between the compressor housing and diffuser. Such leakage interferes with the efficiency of a turbocharger.
Therefore, a need exists for improved turbocharger compressor housings and related methods.